"The Earth’s oceans, which have absorbed carbon dioxide from fuel emissions since the dawn of the industrial era, have recently grown less efficient at sopping it up, new research suggests.

Emissions from the burning of fossil fuels began soaring in the 1950s, and oceans largely kept up, scientists say. But the growth in the intake rate has slowed since the 1980s, and markedly so since 2000, the authors of a study write in a report in Thursday’s issue of Nature.

The research suggests that the seas cannot indefinitely be considered a reliable 'carbon sink' as humans generate heat-trapping gases linked to global warming.

The slowdown in the rise of the absorption rate resulted from a gradual change in the oceans’ chemistry, the study found. 'The more carbon dioxide the ocean absorbs, the more acidic it becomes and the less carbon dioxide it can absorb,' said the study’s lead author, Samar Khatiwala, a research scientist at the Lamont-Doherty Earth Observatory of Columbia University and a professor at the Georgia Institute of Technology."